The present disclosure relates to a wireless power transmission method, a wireless power transmission apparatus, and a wireless charging system in a wireless power transmission field, and there is provided a communication method of a wireless power receiver performing communication with a wireless power transmitter using a plurality of slots, and the communication method may include transmitting control information to the wireless power transmitter within any one of the plurality of slots, receiving an ACK signal from the wireless power transmitter in response to the control information, performing communication with the wireless power transmitter using the any one slot, and determining the position of the any one of the plurality of slots when the ACK signal is received, wherein the position of the any one slot is determined through the counting of the remaining slots existing subsequent to the any one of the plurality of slots.